We have developed a measurement methodology that can estimate the capacity of
Internet paths. The methodology has been implemented in a tool called
Pathrate.
An important feature of Pathrate is that it is robust to cross traffic effects, meaning
that it can
measure the path capacity even when the path is significantly loaded. This is crucial,
since the hardest paths to measure are the heavily loaded ones.
For more information about how Pathrate works, you can read the following
paper:
``Packet Dispersion Techniques and Capacity Estimation''
(to appear in the Transactions on Networking).
An earlier version of this paper appeared at Infocom 2001 with the title:
``What do Packet Dispersion Techniques Measure?''.

Pathrate is based on the dispersion of packet pairs and
packet trains. To make a rather long story very short,
we use many packet pairs (with packets of variable size)
to uncover a set of possible "capacity modes". Then,
we use long packet trains to estimate the so called "Asymptotic
Dispersion Rate" R. We know that the capacity of the path
will be larger than R, and so this gives us a hint about which
local modes to reject. From the modes that are higher than
R, we choose the one that is the strongest and narrowest.